Summary

Description

Filaments are simple, tapering towards the base and up to 10 cm long. It forms a very fine felt-like covering that varies in colour from dark green to purple and adheres closely to damp, shady surfaces. In good years this 'felt' is dark and conspicuous but in others barely detectable. Growth varies seasonally and is maximum in the early months of the year.

Recorded distribution in Britain and Ireland

Isolated records from the Shetland Islands, east and south coasts of England, Northern Ireland, the Firth of Clyde and the outer Hebrides.

Global distribution

Uncommon around the British Isles. Distributed around Europe and also the Pacific Coast of North America and the Canadian Arctic South.

Habitat

The filamentous phase occurs on rocks in the intertidal and on submerged rocks and wood surfaces. The Codiolum-like phase, forms, soft dark green turfs over large areas on the upper shore where it may be wetted at every tide or left exposed for several days at a time.

Depth range

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Identifying features

This species exhibits three different types of thallus depending on environmental conditions.

Varies from green to purple in colour.

Large cell size (0.1-0.5 mm).

Additional information

The large cell size of this species distinguishes it from other Ulothrix and Urospora species.
The three varieties of thallus include, filamentous; dwarf filamentous and unicellular Codiolum-like.

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